In the United States steel industry, direct current (DC) motors having drum-shoe brakes are predominately used for crane drives. Such drum-shoe brakes pose significant maintenance problems for the steel mills due to the necessity of frequent adjustments, the existence of thermal limitations, and the extreme difficulties encountered during servicing. Drum-shoe brakes are given to high wear rates, requiring frequent servicing and shoe replacement. Typically, these brakes are in areas which are difficult to access, being associated with cranes in elevated locations. Additionally, the brake shoes are both heavy and cumbersome. Furthermore, the prior art process of shoe replacement was a lengthy process that was frequently undertaken. One problem with replacing the drum brakes is that the position and area allotted for crane drive brakes is rather fixed, thus requiring the brake to fit into a defined and somewhat limited envelope. Accordingly, any improvement or modification to the brake system must necessarily be confined to that same envelope.
Crane travel drives typically employ hydraulic drum brakes that are controlled by a foot pedal. Springs must be provided such that when the pedal is released, it returns to its initial position. One disadvantage with this system is that the force of the springs must overcome back pressure in a check valve. Another disadvantage with the hydraulic drum brake system is the relatively large pedal stroke required to apply the brake. Such a large pedal stroke requires a large amount of hydraulic fluid to be pressurized and moved through the system. As such, more frequent adjustments are required to maintain the system in proper working order. Accordingly, it is desirable to devise a disk brake assembly in substantially the same general envelope as that employed by the prior art drum brake that has a shorter stroke and the capability to be easily serviced. It is also desirable to devise such a disk brake assembly which can accommodate the axial movement common in D.C. mill motors.